Motor control



March 1931: H. R. EILERTSEN MOTOR CONTROL Filed June 9, 1928 /NVENTOR awaiikgx K A" TORNEYI so'g si eci.portien'o'fisaid u:

Patented Mar. 10, 1931 UNITED STATES PATENT OFFICE HENRY R. EI'LEBTEN, OF SOUND BEACH, CONNECTICUT, ASSIGNOB, BY MESlN'E ASSIGN- IENTS, TO CUTLER-HAMMER INC., 01 KILWA'QKEE, WISCONSIN, A CORPORATION or DELAWARE MOTOR CONTROL Application filed June 8, 1928. SerialNo. 284,097.

This invention relates to improvements in motor control.

More particularly, the invention relates to improvements in variable voltage systems of control for one or more motors.

The invention has among its objects to provide for high torque starting of the controlled motor 'or motors by increasing the field strength of the supply generator and to pro- 0 vide for automatic field weakening of the generator for a reduced voltage following starting of the controlled motor or motors.

A further object is to provide for temporary reduction of the impedance of the field circuit of the supply generator when 1n1t1ally completed whereby the generator field strength will build up more rapidly to the value desired for starting the controlled motor or motors.

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawing illustrates diagrammatically one embodiment of the invention which will now be described, it being understood that the system illustrated may be modified in various respects without departing from the scope of the appended claims.

The system illustrated comprises a generator G driven by an induction motor M, controlled motors M and M to be su plied by the generator and an exeiter E riven by motor M to supply the field windings of machines G, M and M and also certain control instrumentalities hereinafter described. The field windings of motors M and M are shown connected in parallel directly across the exciter E, but as will be understood these field windings may in practice he provided with rheos'tats or other control meansto afiord re 'lation of the speeds of said motors. e generator field F has in circuit therewith a, rheostat R to afford regulation thereof at will, and a resistance R which is normally excluded from circuit, and which, as will appear, is'adapted to be included in circuit followingstartin-g of either motor. As will be un erstood; the v,i'lotal ydesired resistance vmight be incorporatedinfrehostat R, any de- -l )eing used-in lieu of resistance R Also, as will be understood, the generator field may in practice be provided with reversing connections, although for simplicity of illustration said field is shown as non-reversible.

The generator control means comprises an electro-responsive switch 1 having main contacts 2 in circuit between the generator armature and motors M and M and auxiliary contacts 3 to complete the field circuit of the generator upon response of said switch to engage its main contacts. Also, the generator control means comprises an electroresponsive relay 4 normally short-circuiting the resistance B, said relay havinga dash pot 5 or other preferred means for delaying its operation when energized.

As will appear, relay 4 is not energized until the generator connections are established and one or more of the motors connected to the generator, with the result that the generator will be caused to subject the controlled motor or motors to a relatively high voltage for starting. Also, as will be apparent, exclusion of t e resistance R reduces the impedance of the field circuit of the generator whereby the generator field strength will build up more quickly to the value desired. On the other hand, the relay, as will hereinafter appear, is energized at the instant of completing the generator and motor connections aforementioned and accordingly said relay will function after a temporary period to include resistance R for reduction of the generator voltage as is desired after starting of the controlled motor or motors. In this connection it is to be understood that relay 4 is designed and adjusted to afford anv opportunity'for the generator field strength to build up and hi the controlled motor or motors to start prior to inclusion of resistance R. Also, it is to be understood that any other preferred means might be employed for automatically including resistance R following starting of the controlled motor or motors.

The controlled motors M and M are respectively provided with knife switches 6 and 7 and with electroresponsive switches 8 and 9. The knife switches are of the double pole necting either motor, assuming closure of its respective knife switch. y

The remaining control instrumentalities comprise an electroresponsive relay 10, a push button switch 11 controlling said rela to effect starting and running of motors 1 and M or either of the same according to the settings of'the knife switches 6 and I, push buttons 12 and 13 to effect inching operations of motors M and M selectively, and a stop push button switch 14.

Assuming depression of ush button switch om the left hand side of the exciter by conductor 16 through push button switch 14 b conductors 17, 18 and 19 through the win in of switch 8 by conductor 20 through push utton switch 12 by conductor 21 to the right hand side of the exciter. Switch 8 is thus caused to respond to connect motor M .across the lines supplied by the generator, assuming prior closure of knife switch 6. Also, switch 8 through its auxiliary contacts 8 completes an energizing circuit for switch 1 causing said switch to respond to complete the armature and field connections of the generaton This circuit may be traced from push button switch 14 by conductor 17 through the winding of switch 1 by conductor 22 through the auxiliary contacts 8 of switch 8 by conductor. 23 to conductor 21.

Depression of push button switch 12 alsoestablishes a circuit from push button switch 14 by conductor 17 throu h the operating winding of relay 4 by cons through push button switch 12 to conductor 21. Accordingly followin establishment of the connections of motor 1 relay 4 is caused to respond subject to the time element of dash pot 5, with the results aforedescribed. Assuming depression of ush button switch 13 circuit may be traced mm the left hand side of the exciter through push button switch 14 by conductors 17, 18 and 26 through the winding of switch 9 by conductor 27 throu h push button switch 13 by conductor 21 to t e right hand side of the exciter. Thus switch 9 is caused to respond to connect motor M across the linesfiup lied by the generator assuming previous clbsure of knife switch 7 and switch 9 in closing, like switch 8, completes the energizin circuit of the nerator control switch 1. is circuit ma traced through push button switch 14 an the winding 0 switch 1 by conductor 22' as aforedescribed and thence through auxiliary contacts. 9' of switch 9 by conductor 23 to-conductor 21.

Also, depression of push-button switch 13 completes the enelgiz'mg circuit of relay 4 with the results a oredescribed. The chairgizing circuit of relay 4 may be traced from uctors 24 and 25 h push button switch 14 throu h the winding of said relay as aforedescribe and thence by conductors 24 and 25 through push button switch 13 to conductor 21.

As will be understood, the push button switches 12 and 13 efl'ect continued operation of their respective motors only so long as said switches are held depressed. Eac of these switches when released effects deenergization of all windings previously energized thereby, including the windin of the generator control switch 1 and r ay' 4.

Push button switch 11. when depressed completes a circuit from the left hand side of the exciter through ush button switch 14 by conductor 28 throug the winding of relay 10 by conductor 29 throughsaid push button switch 11 to conductor 21 and thence back to the exciter. Relay 10 is thus caused to respond and the same upon responding completes for itself a maintaining circuit extending from conductor 29 through a resistance r and contacts 10' of said relay by conductor 30 to conductor 21. Thus the relay will remain energized upon release of push button switch 11. 2

Relay 10 when energized also establishes energizing. circuits for the motor control switches 8 and 9 and relay 4, and throufgh energization of switches 8 and 9 provides or energization of the generator control switch,

as heretofore described. The energizing circuit for the winding of switch 8 may be traced from the exciter through said wind ng to conductor 20, as heretofore described, and thence by conductor 31 through contacts 10 of relay 10 by conductors 30 and 21 back tothe exciter. e energizing circuit of switch 9 may be traced from the exciter through the winding of said switch to conductor 27 as heretofore described and thence by conductor 32 through the contacts 10 of relay 10 by conductors 30 and 21 back to the exciter. The energizingcircuit for relay 4 may be traced from conductor 24 by conductor 33 through contacts 10" of relay 10 by conductors 30 and 21 to the exciter. A

Thus upon depression of push button switch 11 either or both motors may be started, according to the settings of the knife switches 6 and 7 and the connected motor or motors will continue to operate upon release of the push button switch 11. On the other hand, all of the electroresponsive switches may be deenergized at will for stepping by depression of the stop push button switch 14.

As will be obvio the generator field circuit maybe traced m the left handside of the exciter by conductor 16 to and through the field F by conductor 34 through the aux iliary contacts 3 of switch 1- by conductor 35 through rheostat R and resistance R it); conductor 36' to the ht hand side of 0 exciter, or. alternativ y from'the rheostat R i'lor anal H be supp niole for field 1e 1 nned interval rage system of a generator, a pi to establish circuit and said r ctors ratio field regula rag tor controlled by the iordine; a strengthened. or sitar-fling,- any one or thereatter ejecting wonialically subject to a tags system or motor generat r, field refer, means to .ueans controlled by is a git en amount resistance when said circuit is i tablished and r, such resistance subject to delay.

voltage system of mot-or nation, a generator, field regruia lug means therefor including a resist ance and an electroresponsive relay normally short-circuiting said resistance and having 'nieans affording a predetermined time eleinent incident to its response to include said resistance, and means to establish amotor circuit to be supplied by said generator and also to establish an energizing circuit for said relay;

5 in a variable voltage system of motor so control, in combination, a generator, field regulating means there-for including a rcsistance and an electroresponsive relay normally short-circuiting said resistance and having means affording a predetermined time element incident to its response to include said resistance, and means to selectively establish all or any one of a plurality of motor circuits to be supplied by said generator andalso to establish an energizing circuit for said 60 relay when establishing all or any one of said motor circuits. 1'

In witness whereof, I have hereunto subscribed my name. I

HENRY R. EILERTSEN. 

